U.S. patent application number 15/040549 was filed with the patent office on 2017-08-10 for systems and methods for detecting turn-to-turn faults in windings.
The applicant listed for this patent is General Electric Company. Invention is credited to Mohammad Reza Dadash Zadeh, Sarasij Das, Tarlochan Sidhu, Zhiying Zhang.
Application Number | 20170227591 15/040549 |
Document ID | / |
Family ID | 58098698 |
Filed Date | 2017-08-10 |
United States Patent
Application |
20170227591 |
Kind Code |
A1 |
Zhang; Zhiying ; et
al. |
August 10, 2017 |
SYSTEMS AND METHODS FOR DETECTING TURN-TO-TURN FAULTS IN
WINDINGS
Abstract
Embodiments of the disclosure relate to detecting turn-to-turn
faults in one or more windings of various objects. In one
implementation, a fault detector receives a set of current
measurements associated with a transformer and uses these
measurements to execute a procedure for detecting a turn-to-turn
fault in the transformer. The procedure can include dividing a
steady-state differential current value by a steady-state voltage
value to obtain one or more compensating factors, determining a
magnetizing current amplitude indicator by multiplying the
steady-state voltage value by the one or more compensating factors,
determining a compensated differential current value by combining
the steady-state differential current value with a modifier value
that incorporates the magnetizing current amplitude indicator,
comparing the compensated differential current value against a
threshold value, and declaring an occurrence of the turn-to-turn
fault in the transformer when the compensated differential current
value exceeds the threshold value.
Inventors: |
Zhang; Zhiying; (Markham,
CA) ; Das; Sarasij; (Bangalore, IN) ; Sidhu;
Tarlochan; (Ajax, CA) ; Dadash Zadeh; Mohammad
Reza; (Irvine, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Family ID: |
58098698 |
Appl. No.: |
15/040549 |
Filed: |
February 10, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01R 31/52 20200101;
G01R 31/50 20200101; G01R 31/62 20200101; H02H 3/165 20130101; H02H
7/042 20130101; H02H 7/045 20130101; G01R 31/72 20200101 |
International
Class: |
G01R 31/02 20060101
G01R031/02; H02H 7/04 20060101 H02H007/04; H02H 7/045 20060101
H02H007/045; H02H 3/16 20060101 H02H003/16 |
Claims
1. A system comprising: a transformer; a first current monitoring
element configured to provide a first current measurement based on
monitoring a primary winding current of the transformer; a second
current monitoring element configured to provide a second current
measurement based on monitoring a secondary winding current of the
transformer; and a fault detector configured to receive each of the
first current measurement and the second current measurement and to
detect using the first current measurement and the second current
measurement, a turn-to-turn fault in the transformer by executing a
procedure comprising: determining a steady-state differential
current value; determining a steady-state voltage value;
determining one or more compensating factors by dividing the
steady-state differential current value by the steady-state voltage
value; determining a magnetizing current amplitude indicator by
multiplying the steady-state voltage value by the one or more
compensating factors; determining a compensated differential
current value by combining the steady-state differential current
value with a modifier value, the modifier value incorporating the
magnetizing current amplitude indicator; comparing the compensated
differential current value against a threshold value; declaring an
occurrence of the turn-to-turn fault in the transformer when the
compensated differential current value exceeds the threshold value;
and executing a remedial operation comprising at least one of
transmitting an alarm or operating a protection relay.
2. The system of claim 1, wherein the modifier value is equal to
the magnetizing current amplitude indicator.
3. The system of claim 2, wherein combining the steady-state
differential current value with the modifier value comprises
subtracting the modifier value from the steady-state differential
current value.
4. The system of claim 3, wherein an amplitude of the magnetizing
current amplitude indicator is directly proportional to an
amplitude of an operating voltage of the transformer.
5. The system of claim 4, wherein the occurrence of the
turn-to-turn fault in the transformer is declared when the
compensated differential current value exceeds the threshold value
for a predetermined period of time.
6. The system of claim 5, further comprising a user interface
configured to accept a user input indicative of the predetermined
period of time.
7. The system of claim 1, wherein the transformer is a multi-phase
transformer and each of the primary winding current and the
secondary winding current corresponds to a first pair of windings
among a plurality of windings of the multi-phase transformer.
8. The system of claim 7, wherein the fault detector detects the
turn-to-turn fault when present in any one of the plurality of
windings of the multi-phase transformer.
9. The system of claim 1, wherein the transformer is a three-phase
transformer having at least two sets of windings and the fault
detector executes the procedure for each phase of the three-phase
transformer.
10. A system comprising: a multi-phase transformer; an electrical
current monitoring system configured to provide a set of primary
electrical current measurements based on monitoring each of a
plurality of primary winding currents of the multi-phase
transformer and a set of secondary electrical current measurements
based on monitoring each of a plurality of secondary winding
currents of the multi-phase transformer; and a fault detector
configured to receive the set of primary electrical current
measurements and the set of secondary electrical current
measurements and to detect using the set of primary electrical
current measurements and the set of secondary electrical current
measurements, a turn-to-turn fault in the multi-phase transformer
by executing a procedure comprising: determining a steady-state
differential current value for each phase of the multi-phase
transformer; determining a steady-state differential voltage value
for each phase of the multi-phase transformer; determining one or
more compensating factors by dividing the steady-state differential
current value by the steady-state voltage value for each phase of
the multi-phase transformer; determining a magnetizing current
amplitude indicator for each phase of the multi-phase transformer
by multiplying a respective steady-state voltage value by one or
more compensating factors; determining a compensated differential
current value for each phase of the multi-phase transformer by
combining a respective steady-state differential current value with
a respective modifier value, each respective modifier value
incorporating a respective magnetizing current amplitude indicator;
comparing the compensated differential current value for each phase
of the multi-phase transformer against a threshold value for each
phase of the multi-phase transformer; declaring an occurrence of
the turn-to-turn fault in the transformer when at least one of the
compensated differential current values exceeds the threshold
value; and executing a remedial operation comprising at least one
of transmitting an alarm or operating a protection relay.
11. The system of claim 10, wherein the respective modifier value
is equal to the respective magnetizing current amplitude
indicator.
12. The system of claim 11, wherein combining the respective
steady-state differential current value with the respective
modifier value comprises subtracting the respective modifier value
from the respective steady-state differential current value.
13. The system of claim 12, wherein an amplitude of the respective
magnetizing current amplitude indicator is directly proportional to
an amplitude of a respective phase operating voltage of the
transformer.
14. The system of claim 13, wherein the occurrence of the
turn-to-turn fault in the transformer is declared when the at least
one of the compensated differential current values exceeds the
threshold value for a predetermined period of time.
15. The system of claim 14, further comprising a user interface
configured to accept a user input indicative of the predetermined
period of time.
16. The system of claim 10, wherein the transformer is a
three-phase transformer.
17. The system of claim 16, wherein the fault detector detects the
turn-to-turn fault when present in any one of the plurality of
windings of the three-phase transformer.
18. A method comprising: receiving in a fault detector, a first
current measurement based on monitoring a primary winding current
of a transformer; receiving in the fault detector, a second current
measurement based on monitoring a secondary winding current of a
transformer; using the first current measurement and the second
current measurement to determine a steady-state differential
current value and a steady-state voltage value; determining one or
more compensating factors by dividing the steady-state differential
current value by the steady-state voltage value; determining a
magnetizing current amplitude indicator by multiplying the
steady-state voltage value by the one or more compensating factors;
determining a compensated differential current value by combining
the steady-state differential current value with a modifier value,
the modifier value incorporating the magnetizing current amplitude
indicator; comparing the compensated differential current value
against a threshold value; declaring an occurrence of the
turn-to-turn fault in the transformer when the compensated
differential current value exceeds the threshold value; and
executing a remedial operation comprising at least one of
transmitting an alarm or operating a protection relay.
19. The method of claim 18, wherein the modifier value is equal to
the magnetizing current amplitude indicator.
20. The method of claim 19, wherein combining the steady-state
differential current value with the modifier value comprises
subtracting the modifier value from the steady-state differential
current value.
Description
FIELD OF THE DISCLOSURE
[0001] This disclosure relates to winding fault detectors, and more
particularly, to turn-to-turn winding fault detector systems and
methods.
BACKGROUND OF THE DISCLOSURE
[0002] Winding coils are incorporated into a wide variety of
products, for example, into inductors and transformers. More
particularly, in electrical power transmission systems, various
components, for example, a power transformer or a shunt reactor,
can include one or more winding coils. Various types of faults can
occur in these windings when in use. Some of these faults, for
example, a short circuit between the output terminals of a power
transformer are more readily detectible than other faults such as,
an internal short circuit between a few turns of a primary winding
or a secondary winding of the power transformer. The internal short
circuit between the few turns may not necessarily result in a
significant change in the amount of current being delivered by the
power transformer to a power transmission line that is coupled to
the power transformer. However, if timely remedial action is not
taken, such a fault can eventually develop into a major fault that
can severely impact power transmission through the power
transmission line.
[0003] Conventional fault detection devices which are typically
configured to detect significant current changes in various types
of windings may be unable to effectively detect small turn-to-turn
faults in such windings. More particularly, conventional fault
detection devices may lack adequate sensitivity to detect changes
in low amplitude differential currents that are indicative of
turn-to-turn faults. Consequently, some solutions have been
proposed that are directed at detecting turn-to-turn faults using
other techniques. For example, one conventional solution generally
pertains to fault detection in a power transformer by using a
negative sequence based algorithm incorporating a differential
principle, while another conventional solution generally pertains
to fault detection in a power transformer by using a negative
sequence based algorithm incorporating a direction comparison
principle. Such conventional solutions using negative sequence
differential currents for fault detection can be impacted by
various system imbalance conditions that can affect the sensitivity
and the reliability of the detection process. Further, even when a
fault is detected, the precise location of the fault in terms of a
particular phase in a multi-phase transformer system may not be
identifiable.
BRIEF DESCRIPTION OF THE DISCLOSURE
[0004] Embodiments of the disclosure are directed generally to
systems and methods for detecting turn-to-turn faults in
winding.
[0005] A first exemplary system in accordance with an embodiment of
the disclosure can include a transformer, a first current
monitoring element, a second current monitoring element and a fault
detector. The first current monitoring element can be configured to
provide a first current measurement based on monitoring a primary
winding current of the transformer. The second current monitoring
element can configured to provide a second current measurement
based on monitoring a secondary winding current of the transformer.
The fault detector can be configured to receive each of the first
current measurement and the second current measurement and to
detect using the first current measurement and the second current
measurement, a turn-to-turn fault in the transformer by executing a
procedure that can include determining a steady-state differential
current value, determining a steady-state voltage value,
determining one or more compensating factors by dividing the
steady-state differential current value by the steady-state voltage
value, determining a magnetizing current amplitude indicator by
multiplying the steady-state voltage value by the one or more
compensating factors, determining a compensated differential
current value by combining the steady-state differential current
value with a modifier value, the modifier value incorporating the
magnetizing current amplitude indicator, comparing the compensated
differential current value against a threshold value, declaring an
occurrence of the turn-to-turn fault in the transformer when the
compensated differential current value exceeds the threshold value,
and executing a remedial operation comprising at least one of
transmitting an alarm or operating a protection relay.
[0006] A second exemplary system in accordance with an embodiment
of the disclosure can include a multi-phase transformer, an
electrical current monitoring system, and a fault detector. The
electrical current monitoring system can be configured to provide a
set of primary electrical current measurements based on monitoring
each of a plurality of primary winding currents of the multi-phase
transformer and a set of secondary electrical current measurements
based on monitoring each of a plurality of secondary winding
currents of the multi-phase transformer. The fault detector can be
configured to receive the set of primary electrical current
measurements and the set of secondary electrical current
measurements and to detect using the set of primary electrical
current measurements and the set of secondary electrical current
measurements, a turn-to-turn fault in the multi-phase transformer
by executing a procedure that can include determining a
steady-state differential current value for each phase of the
multi-phase transformer, determining a steady-state differential
voltage value for each phase of the multi-phase transformer,
determining one or more compensating factors by dividing the
steady-state differential current value by the steady-state voltage
value for each phase of the multi-phase transformer, determining a
magnetizing current amplitude indicator for each phase of the
multi-phase transformer by multiplying a respective steady-state
voltage value by one or more compensating factors, determining a
compensated differential current value for each phase of the
multi-phase transformer by combining a respective steady-state
differential current value with a respective modifier value, each
respective modifier value incorporating a respective magnetizing
current amplitude indicator, comparing the compensated differential
current value for each phase of the multi-phase transformer against
a threshold value for each phase of the multi-phase transformer,
declaring an occurrence of the turn-to-turn fault in the
transformer when at least one of the compensated differential
current values exceeds the threshold value, and executing a
remedial operation comprising at least one of transmitting an alarm
or operating a protection relay.
[0007] An exemplary method in accordance with an embodiment of the
disclosure can include receiving in a fault detector, a first
current measurement based on monitoring a primary winding current
of a transformer, receiving in the fault detector, a second current
measurement based on monitoring a secondary winding current of a
transformer, using the first current measurement and the second
current measurement to determine a steady-state differential
current value and a steady-state voltage value, determining one or
more compensating factors by dividing the steady-state differential
current value by the steady-state voltage value, determining a
magnetizing current amplitude indicator by multiplying the
steady-state voltage value by the one or more compensating factors,
determining a compensated differential current value by combining
the steady-state differential current value with a modifier value,
the modifier value incorporating the magnetizing current amplitude
indicator, comparing the compensated differential current value
against a threshold value, declaring an occurrence of the
turn-to-turn fault in the transformer when the compensated
differential current value exceeds the threshold value, and
executing a remedial operation comprising at least one of
transmitting an alarm or operating a protection relay.
[0008] Other embodiments and aspects of the disclosure will become
apparent from the following description taken in conjunction with
the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Having thus described the disclosure in general terms,
reference will now be made to the accompanying drawings, which are
not necessarily drawn to scale, and wherein:
[0010] FIG. 1 illustrates an example three-phase power line system
that can include a turn-to-turn fault detector configured to detect
one or more turn-to-turn faults in a three-phase shunt reactor in
accordance with an exemplary embodiment of the disclosure.
[0011] FIG. 2 illustrates an example phase diagram pertaining to
detecting one or more turn-to-turn faults in the three-phase shunt
reactor shown in FIG. 1 on the basis of phase angle
information.
[0012] FIG. 3 illustrates an example power transmission system that
can include a turn-to-turn fault detector system configured to
detect a turn-to-turn fault in a single phase transformer in
accordance with another exemplary embodiment of the disclosure.
[0013] FIG. 4 illustrates an example power transmission system that
can include a turn-to-turn fault detector system configured to
detect a turn-to-turn fault in a three-phase transformer in
accordance with another exemplary embodiment of the disclosure.
[0014] FIG. 5 illustrates an example equivalent circuit diagram
applicable to each of the single phase transformer shown in FIG. 3
and the three-phase transformer shown in FIG. 4.
[0015] FIG. 6 illustrates an exemplary turn-to-turn fault detector
in accordance with an exemplary embodiment of the disclosure.
[0016] FIGS. 7A and 7B illustrate a flowchart of an example method
of using a turn-to-turn fault detector to detect a fault in one or
more windings of a three-phase shunt reactor in accordance with an
exemplary embodiment of the disclosure.
[0017] FIGS. 8A and 8B illustrate a flowchart of an example method
of using a turn-to-turn fault detector to detect a turn-to-turn
fault in one or more windings of a transformer in accordance with
another exemplary embodiment of the disclosure.
DETAILED DESCRIPTION OF THE DISCLOSURE
[0018] The disclosure will be described more fully hereinafter with
reference to the accompanying drawings, in which exemplary
embodiments of the disclosure are shown. This disclosure may,
however, be embodied in many different forms and should not be
construed as limited to the exemplary embodiments set forth herein;
rather, these embodiments are provided so that this disclosure will
satisfy applicable legal requirements. Like numbers refer to like
elements throughout. It should be understood that certain words and
terms are used herein solely for convenience and such words and
terms should be interpreted as referring to various objects and
actions that are generally understood in various forms and
equivalencies by persons of ordinary skill in the art. For example,
it should be understood that the word "line" as used herein
generally refers to an electrical conductor, for example, a wire or
an electrical power cable. Furthermore, the word "example" as used
herein is intended to be non-exclusionary and non-limiting in
nature. More particularly, the word "exemplary" as used herein
indicates one among several examples, and it should be understood
that no undue emphasis or preference is being directed to the
particular example being described.
[0019] In terms of a general overview, certain embodiments of the
systems and methods described herein are directed to a fault
detector that can be used to detect one or more turn-to-turn faults
in a coil winding. As is known, coil windings are ubiquitously
incorporated into a wide array of products. However, in the
interest of brevity, only two products, specifically a three-phase
shunt reactor and a power transformer, are used herein to describe
various embodiments and aspects in accordance with the
disclosure.
[0020] Attention is first drawn to FIG. 1, which illustrates an
example three-phase power line system 100 that can include a
turn-to-turn fault detector 120 configured to detect one or more
turn-to-turn faults in a three-phase shunt reactor 155 in
accordance with an exemplary embodiment of the disclosure.
Three-phase power line system 100 can be used to propagate electric
power over three power lines 101, 102, and 103 in a three-phase
configuration as is known in the art. Each of the three power lines
101, 102, and 103 can be coupled to the three-phase shunt reactor
155 that is deployed in a manner that is known in the art. The
three-phase shunt reactor 155 can include three windings that are
collectively coupled to ground via a node 118. A first winding 114
of the three windings in the three-phase shunt reactor 155 is
coupled to the power line 101 via a first current monitoring
element 125 and a first isolating switch 140. The first isolating
switch 140 can be controlled by the turn-to-turn fault detector 120
via a control line 113 in order to isolate the first winding 114
from the power line 101 when a turn-to-turn fault is detected in
the first winding 114. A second winding 116 of the three windings
in the three-phase shunt reactor 155 is coupled to the power line
102 via a second current monitoring element 130 and a second
isolating switch 145. The second isolating switch 145 can be
controlled by the turn-to-turn fault detector 120 via the control
line 113 (or via a separate control line that is not shown) in
order to isolate the second winding 116 from the power line 102
when a turn-to-turn fault is detected in the second winding 116. A
third winding 117 of the three windings in the three-phase shunt
reactor 155 is coupled to the power line 103 via a third current
monitoring element 135 and a third isolating switch 150. The third
isolating switch 150 can be controlled by the turn-to-turn fault
detector 120, via the control line 113 (or via a separate control
line that is not shown) in order to isolate the third winding 117
from the power line 103 when a turn-to-turn fault is detected in
the third winding 117. It should be understood that more than one
of the three optional switches 140, 145, and 150 (each of which can
be implemented in the form of a relay, for example) can be operated
by the turn-to-turn fault detector 120 when one or more
turn-to-turn faults are detected in one or more of the three
windings 114, 116, and 117. Furthermore, in place of using the
three isolating switches, other protection elements and
configurations can be used to provide remedial action upon
detecting one or more turn-to-turn faults in one or more of the
three windings 114, 116, and 117.
[0021] The first current monitoring element 125 can be used to
monitor the power line 101 and to output a current measurement that
is a scaled-down version of a first phase current that is routed
from the power line 101 into the first winding 114 of the
three-phase shunt reactor 155 when three-phase electric power is
being transmitted through the three-phase power line system 100.
The current measurement output of the current monitoring element
125 is coupled into the turn-to-turn fault detector 120 via a line
109. The second current monitoring element 130 can be similarly
used to monitor the power line 102 and to output a current
measurement that is a scaled-down version of a second phase current
that is routed from the power line 102 to the second winding 116 of
the three-phase shunt reactor 155 when three-phase electric power
is being transmitted through the three-phase power line system 100.
The current measurement output of the current monitoring element
130 is coupled into the turn-to-turn fault detector 120 via a line
111. The third current monitoring element 135 can also be similarly
used to monitor the power line 103 and to output a current
measurement that is a scaled-down version of a third phase current
that is routed from the power line 103 to the third winding 117 of
the three-phase shunt reactor 155 when three-phase electric power
is being transmitted through the three-phase power line system 100.
The current measurement output of the current monitoring element
135 is coupled into the turn-to-turn fault detector 120 via a line
112.
[0022] With further reference to the three-phase shunt reactor 155,
in an exemplary embodiment in accordance with the disclosure, the
three windings 114, 116, and 117 can be collectively contained
within a single enclosure. Furthermore, the three windings 114,
116, and 117 can be provided in various configurations such as, for
example, a .DELTA. configuration or a wye configuration. In another
exemplary embodiment in accordance with disclosure, each of the
three windings 114, 116, and 117 can be contained in three separate
enclosures. In yet another exemplary embodiment in accordance with
disclosure, two or more of the three windings 114, 116, and 117 can
be contained in a second enclosure that is different than a first
enclosure in which the remaining of the three windings 114, 116,
and 117 is contained. In yet another exemplary embodiment in
accordance with disclosure, one or more additional windings can be
provided in addition to the three windings 114, 116, and 117. For
example, a fourth winding can be coupled between the node 118 and
ground. The turn-to-fault detector 120 can be used to detect one or
more turn-to-turn faults in one or more of these various windings
in accordance with the disclosure.
[0023] Turning now to other monitoring elements in the three-phase
power line system 100, a first voltage monitoring element 105 can
be used to monitor the power line 101 and to output a voltage
measurement that is a scaled-down version of a first phase voltage
present on the power line 101 when three-phase electric power is
transmitted through the three-phase power line system 100. The
voltage measurement output of the voltage monitoring element 105 is
coupled into the turn-to-turn fault detector 120 via a line 106. A
second voltage monitoring element 115 can be used to monitor the
power line 102 and to output a voltage measurement that is a
scaled-down version of a second phase voltage present on the power
line 102 when three-phase electric power is transmitted through the
three-phase power line system 100. The voltage measurement output
of the voltage monitoring element 110 is coupled into the
turn-to-turn fault detector 120 via a line 107. A third voltage
monitoring element 115 can be used to monitor the power line 103
and to output a voltage measurement that is a scaled-down version
of a third phase voltage present on the power line 103 when
three-phase electric power is transmitted through the three-phase
power line system 100. The voltage measurement output of the
voltage monitoring element 115 is coupled into the turn-to-turn
fault detector 120 via a line 108.
[0024] The turn-to-turn fault detector 120 includes various
elements that will be described below in more detail using another
figure. Operatively, the turn-to-turn fault detector 120 is
configured to execute a procedure that uses a differential
protection algorithm to detect one or more turn-to-turn faults in
one or more windings of the three-phase shunt reactor 155. In one
example implementation, the procedure includes using the voltage
measurements provided by the voltage monitoring elements 105, 110,
and 115, and the current measurements provided by the current
monitoring elements 125, 130, and 135 to calculate a difference
value between a voltage-based parameter and a current-based
parameter. The voltage-based parameter is indicative of a
normalized negative voltage imbalance and the current-based
parameter is indicative of a normalized negative current imbalance.
The procedure further includes declaring an occurrence of the
turn-to-turn fault in at least one of the first winding 114, the
second winding 116, or the third winding 117 of the three-phase
shunt reactor 155 when the difference value is not equal to zero.
The difference value is approximately zero under steady state
conditions and no turn-to-turn fault is present in the three
windings 114, 116, and 117. Any small deviation from zero can be
attributed to minor system imbalances that may be present under
normal operating conditions of the three-phase power line system
100. In some exemplary implementations, the occurrence of the
turn-to-turn fault can be declared only when the difference value
exceeds a threshold value.
[0025] Significantly, and in contrast to conventional turn-to-turn
fault detection systems, the turn-to-turn fault detector 120 can be
used to identify a specific faulty phase among the various phases
of a target object, for example, among the three phases in the
three-phase power line system 100. Also, the turn-to-turn fault
detector 120 can be used to identify turn-to-turn faults in various
types of windings without requiring impedance information of the
windings (for example, impedance information pertaining to any of
the three windings 114, 116, and 117) and without requiring
information pertaining to a current flow through a neutral winding
(not shown) of the three-phase shunt reactor 155.
[0026] Furthermore, the turn-to-turn fault detector 120 can provide
a satisfactory level of performance under various operational
conditions of the three-phase power line system 100, for example,
under normal system unbalances, off-nominal system frequencies,
off-nominal system voltages, during load switching, in the presence
of harmonics, and in the presence of faults external to the
three-phase shunt reactor 155. However, in one example
implementation, the turn-to-turn fault detector 120 is configured
to avoid using the differential protection algorithm when one or
more of the current monitoring elements 125, 130, and 135 undergo
one or more of a current saturation condition, a current inrush
condition, or an offline condition.
[0027] Details pertaining to the differential protection algorithm
used by the turn-to-turn fault detector 120 to detect one or more
turn-to-turn faults in one or more windings of the three-phase
shunt reactor 155 can be further understood in view of the
following description based on mathematical equations in accordance
with the disclosure.
I.sub.A=V.sub.A/Z.sub.A;I.sub.B=V.sub.B/Z.sub.B;I.sub.C=V.sub.C/Z.sub.C;
Equation (1)
V.sub.Neg.sub._.sub.Unbal.sub._.sub.Normalized=(V.sub.2/V.sub.1).times.1-
00% Equation (2)
I.sub.Neg.sub._.sub.Unbal.sub._.sub.Normalized=(I.sub.2/I.sub.1).times.1-
00% Equation (3)
I.sub.Neg.sub._.sub.Unbal.sub._.sub.Normalized=(I.sub.A+a.sup.2I.sub.B+a
I.sub.C)/(I.sub.A+a
I.sub.B+a.sup.2I.sub.C).times.100%=[V.sub.A/Z.sub.A+a.sup.2(V.sub.B/Z.sub-
.B)+a(V.sub.C/Z.sub.C)]/[V.sub.A/Z.sub.A+a(V.sub.B/Z.sub.B)+a.sup.2(V.sub.-
C/Z.sub.C)].times.100% Equation (4)
[0028] where V.sub.A, V.sub.B, and V.sub.C are phase voltage
measurements provided to the turn-to-turn detector 120 by the
voltage monitoring elements 105, 110, and 115 respectively;
I.sub.A, I.sub.B, and I.sub.C are phase current measurements
provided to the turn-to-turn detector 120 by the current monitoring
elements 125, 130, and 135; Z.sub.A, Z.sub.B, and Z.sub.C are phase
impedances of the three windings 114, 116, and 117 of the
three-phase shunt reactor 155; V.sub.2 and V.sub.1 are negative
sequence and positive sequence voltages respectively; and I.sub.2
and I.sub.1 are negative sequence and positive sequence currents
respectively. The operator "a" is defined as a unit vector at an
angle of 120 degrees, and can be described as "a"=1.angle.120
degrees.
[0029] The three windings 114, 116, and 117 of the three-phase
shunt reactor 155 are typically identical to one another and have a
symmetrical arrangement. Consequently, when the three-phase power
line system 100 is operating in a steady state,
Z.sub.A=Z.sub.B=Z.sub.C=Z. Thus, from equations (1) through (4), it
can be understood that:
I.sub.Neg.sub._.sub.Unbal.sub._.sub.Normalized=[V.sub.A/Z+a.sup.2(V.sub.-
B/Z)+a(V.sub.C/Z)]/[V.sub.A/Z+a(V.sub.B/Z)+a.sup.2(V.sub.C/Z)].times.100%=-
(V.sub.A+a.sup.2V.sub.B+a V.sub.C)/(V.sub.A+a
V.sub.B+a.sup.2V.sub.C).times.100%=(V.sub.2/V.sub.1).times.100%=V.sub.Neg-
.sub._.sub.Unbal.sub._.sub.Normalized Equation (5)
[0030] where V.sub.Neg.sub._.sub.Unbal.sub._.sub.Normalized and
I.sub.Neg.sub._.sub.Unbal.sub._.sub.Normalized are unit-less
complex quantities expressed in a percentage form.
[0031] A difference value can now be defined in the form of a
variable "Diff" as follows:
Diff=V.sub.Neg.sub._.sub.Unbal.sub._.sub.Normalized-I.sub.Neg.sub._.sub.-
Unbal.sub._.sub.Normalized Equation (6)
[0032] Because Z.sub.A=Z.sub.B=Z.sub.C=Z during steady state
operation,
Diff.sub.stead=0 or Diff.sub.steady.apprxeq.0 Equation (7)
[0033] When a turn-to-turn faults is present in one of the three
windings 114, 116, and 117 of the three-phase shunt reactor 155, an
impedance of the winding having the turn-to-turn fault changes,
thereby resulting in:
V.sub.Neg.sub._.sub.Unbal.sub._.sub.Normalized-I.sub.Neg.sub._.sub.Unbal-
.sub._.sub.Normalized=Diff Equation (8)
[0034] An absolute value of the difference parameter (Diff) can be
used by the turn-to-turn fault detector 120 to declare a fault
condition. In one example implementation, a fault condition can be
declared when the absolute value of the difference parameter (Diff)
exceeds a threshold percentage value "c." The threshold percentage
value "c" can be a settable threshold value that can be set by an
operator of the turn-to-turn fault detector 120.
Fault condition=abs(Diff-Diff.sub.steady)>c Equation (9)
[0035] A fault condition can also be declared by examining vector
representations of phases associated with each of the voltages
V.sub.A, V.sub.B, and V.sub.C. In one exemplary embodiment, this
can be carried out by using the expression
.angle.(Diff-Diff.sub.steady). A faulty "phase A" may be declared
when .angle.(Diff-Diff.sub.steady) is in a range of
180.degree..+-.D, a faulty "phase B" may be declared when
.angle.(Diff-Diff.sub.steady) is in a range of -60.degree..+-.D,
and a faulty "phase C" may be declared when
.angle.(Diff-Diff.sub.steady) is in a range of +60 degrees.+-.D,
where "D" is a limit angle that can be set in a range of 20.degree.
to 60.degree..
[0036] FIG. 2 illustrates an example phase diagram 200 pertaining
to detecting one or more turn-to-turn faults in the three-phase
shunt reactor 155 on the basis of phase angle information. The
range of 180 degrees.+-.D corresponding to "phase A" is indicated
by an arrow 205, the range of -60 degrees.+-.D corresponding to
"phase B" is indicated by an arrow 210, and the range of +60
degrees.+-.D corresponding to "phase C" is indicated by an arrow
215. The turn-to-turn fault detector 120 can be configured to
declare a fault in a particular phase among the three phases A, B,
and C by employing the three ranges shown in the example phase
diagram 200.
[0037] FIG. 3 illustrates an example power transmission system 300
that can include a turn-to-turn fault detector system 120
configured to detect a turn-to-turn fault in the primary and
secondary windings of a single phase transformer 310 in accordance
with another exemplary embodiment of the disclosure. A first
current monitoring element 305 can be used to monitor a primary
current "I.sub.P" that flows via line 306 and into a primary
winding of the single phase transformer 310. The first current
monitoring element 305 provides a scaled-down version of the
primary current to the turn-to-turn fault detector 120 via a line
301. A second current monitoring element 315 can be used to monitor
a secondary current "I.sub.S" that flows out to a line 307 from a
secondary winding of the single phase transformer 310. The second
current monitoring element 315 provides a scaled-down version of
the secondary current to the turn-to-turn fault detector 120 via a
line 302. Additional monitoring elements (not shown) can be used
for monitoring voltages at various nodes of the power transmission
system 300, such as, for example, to provide the turn-to-turn fault
detector 120 with one or more steady-state voltage values or
differential voltage values associated with the primary winding and
the secondary winding of the single phase transformer 310.
[0038] In this exemplary embodiment, the turn-to-turn fault
detector 120 is configured to execute a procedure that includes
using the current values and the voltage values obtained via the
various monitoring elements to determine various steady-state
differential currents and various steady-state voltage values. Each
of the steady-state differential currents typically includes a
steady-state magnetizing current component that is dependent upon
at least one steady-state voltage that is present at a terminal of
the single phase transformer 310.
[0039] In accordance with this disclosure, and in contrast to
conventional implementations, one or more compensating factors (in
the form of one or more modifier values) are combined with the
various steady-state differential current values to compensate for
the steady-state magnetizing current component and also to
compensate for any measurement errors in the steady-state
differential current values. In one example implementation, a
modifier value that is equal to a magnetizing current component
value can be used. The modifier value may be subtracted from a
steady-state differential current value to provide the
compensation.
[0040] The compensated steady-state differential current value can
then be used to detect a turn-to-turn fault, such as, for example,
by comparing a compensated steady-state differential current value
against a reference threshold value. The comparing may be carried
out over a pre-settable period of time that can be pre-set by an
operator, for example.
[0041] Upon detection of a turn-to-turn fault, the turn-to-turn
fault detector 120 can carry out a remedial action. For example,
the turn-to-turn fault detector 120 can provide a first control
signal (via a line 303) to a first breaker 320 in order to isolate
the primary winding of the single phase transformer 310 from the
power line conductor 306. As another example, the turn-to-turn
fault detector 120 can provide a second control signal (via a line
304) to a second breaker 325 in order to isolate the secondary
winding of the single phase transformer 310 from the power line
conductor 307. The turn-to-turn fault detector 120 can also provide
a fault indicator signal via a line 412, to a fault monitoring unit
(not shown) such as, for example, a computer that is located at a
monitoring station, a display device located at the monitoring
station, or an alarm (light, buzzer, siren etc.) located on or near
the turn-to-turn fault detector 120.
[0042] FIG. 4 illustrates a power transmission system 400 that can
include a turn-to-turn fault detector system 120 configured to
detect a turn-to-turn fault in a three-phase transformer 410 in
accordance with another exemplary embodiment of the disclosure. In
this other exemplary embodiment, the three-phase transformer 410 is
shown with three primary windings interconnected in a ".DELTA."
arrangement and three secondary windings interconnected in a "Y"
arrangement, solely as a matter of convenience for purposes of
description. However, it should be understood that the description
provided below in accordance with the disclosure, is equally
applicable to various other configurations and interconnections
associated with the three three-phase transformer 410.
[0043] A first current monitoring element 405 can be used to
monitor a phase "A" primary current "I.sub.AP" that flows via line
401 into a first primary winding of the three-phase transformer
410. The first current monitoring element 405 provides to the
turn-to-turn fault detector 120, via a line 404, a scaled-down
version "I.sub.ap" of the primary current "I.sub.AP." A second
current monitoring element 420 can be used to monitor a phase "B"
primary current "I.sub.BP" that flows via line 402 into a second
primary winding of the three-phase transformer 410. The second
current monitoring element 420 provides to the turn-to-turn fault
detector 120, via a line 406, a scaled-down version "I.sub.bp" of
the primary current "I.sub.BP." A third current monitoring element
435 can be used to monitor a phase "C" primary current "I.sub.CP"
that flows via line 403 into a third primary winding of the
three-phase transformer 410. The third current monitoring element
435 provides to the turn-to-turn fault detector 120, via a line
407, a scaled-down version "I.sub.cp" of the primary current
"I.sub.CP."
[0044] A fourth current monitoring element 415 can be used to
monitor a phase "A" secondary current "I.sub.AS" that is provided
by a first secondary winding of the three-phase transformer 410 to
a line 413. The fourth current monitoring element 415 provides to
the turn-to-turn fault detector 120, a first secondary current
measurement "I.sub.as" that is a scaled-down version of "I.sub.AS."
A fifth current monitoring element 430 can be used to monitor a
phase "B" secondary current "I.sub.BS" that is provided by a second
secondary winding of the three-phase transformer 410 to a line 414.
The fifth current monitoring element 430 provides to the
turn-to-turn fault detector 120, a second secondary current
measurement "I.sub.bs" that is a scaled-down version of "I.sub.BS."
A sixth current monitoring element 445 can be used to monitor a
phase "C" secondary current "I.sub.CS" that is provided by a third
secondary winding of the three-phase transformer 410 to a line 416.
The sixth current monitoring element 430 provides to the
turn-to-turn fault detector 120, a third secondary current
measurement "I.sub.cs" that is a scaled-down version of "I.sub.CS."
In this exemplary embodiment, the three secondary current
measurements ("I.sub.as," "I.sub.bs," and "I.sub.cs") are coupled
into the turn-to-turn fault detector 120 via a line arrangement
that includes line 408, line 409, and line 411.
[0045] Additional monitoring elements (not shown) can be used for
monitoring voltages at various nodes of the power transmission
system 300, for example, to provide the turn-to-turn fault detector
120 with one or more steady-state voltage values or differential
voltage values associated with one or more of the three primary
windings and the three secondary windings of the three-phase
transformer 410.
[0046] The turn-to-turn fault detector 120 is configured to execute
a procedure that includes using the current values and the voltage
values obtained via the various monitoring elements described above
to determine various steady-state differential currents and various
steady-state voltage values. This procedure can be understood in
view of the procedure described above with reference to the power
transmission system 300 shown in FIG. 3, and further in view of the
following description based on mathematical equations in accordance
with the disclosure.
Idiff_A_compensated=Idiff_A-KA*V.sub.RA Equation (10)
Idiff_B_compensated=Idiff_B-KA*V.sub.RB Equation (11)
Idiff_C_compensated=Idiff_C-KA*V.sub.RC Equation (12)
[0047] where V.sub.RA, V.sub.RB, and V.sub.RC are the phase A,
phase B, and phase C voltages on the output side of the three-phase
transformer 410. However, in alternative implementations, the phase
A, phase B, and phase C voltages on the input side of the
three-phase transformer 410 can be used instead. KA, KB, and KC are
coefficients that are used during a steady state operation of the
three-phase transformer 410 in order to make each of
Idiff_A_compensated, Idiff_B_compensated, and Idiff_C_compensated
equal to zero. One or more of each of Idiff_A_compensated,
Idiff_B_compensated, and Idiff_C_compensated will increase to a
value greater than zero when a turn-to-fault exists in one or more
of the respective windings. The coefficients KA, KB, and KC can be
defined as follows:
KA=Idiff_A_steady/V.sub.RA steady Equation (13)
KB=Idiff_A_steady/V.sub.RB steady Equation (14)
KC=Idiff_A_steady/V.sub.RC steady Equation (15)
[0048] An absolute value of each of Idiff_A_compensated,
Idiff_B_compensated, and Idiff_C_compensated can be used by the
turn-to-turn fault detector 120 to declare a fault condition in a
respective phase of the three-phase transformer 410. In one example
implementation, a fault condition can be declared in phase A when
the absolute value of Idiff_A_compensated exceeds (or equals) a
threshold percentage value "a," a fault condition can be declared
in phase B when the absolute value of Idiff_B_compensated exceeds
(or equals) a threshold percentage value "b," and a fault condition
can be declared in phase C when the absolute value of
Idiff_C_compensated exceeds (or equals) a threshold percentage
value "c." In other words, a turn-to-turn fault condition in phase
A is declared when abs(Idiff_A_compensated).gtoreq."a," a
turn-to-turn fault condition in phase B is declared when
abs(Idiff_B_compensated).gtoreq."b," and a turn-to-turn fault
condition in phase C is declared when
abs(Idiff_C_compensated).gtoreq."c." The threshold percentage
values "a," "b," and "c" can be settable threshold values that can
be set, for example, by an operator of the turn-to-turn fault
detector 120.
[0049] Upon detection of a turn-to-turn fault in the three-phase
transformer 410, the turn-to-turn fault detector 120 can carry out
a remedial action. For example, the turn-to-turn fault detector 120
can provide a control signal (via a line 412) to one or more
protection elements (not shown) in order to isolate one or more of
the primary windings from a respective one or more input lines,
and/or to isolate one or more of the secondary windings from a
respective one or more output lines. In some example
implementations, the turn-to-turn fault detector 120 can provide a
fault indicator signal via the line 412 to a fault monitoring unit
(not shown) such as, for example, a computer that is located at a
monitoring station, a display device located at the monitoring
station, or an alarm (light, buzzer, siren etc.) located on or near
the turn-to-turn fault detector 120.
[0050] FIG. 5 illustrates an example equivalent circuit diagram of
the single phase transformer 310 shown in FIG. 3. The input current
I.sub.1 is equal to the output current I.sub.2 (typically with a
phase difference of 180.degree.) if no loss were to be incurred in
the single phase transformer 310. However, in practicality, a
current loss does occur in the single phase transformer 310. This
current loss can be attributed to a magnetizing current I.sub.0
that is shown in the equivalent circuit diagram. The turn-to-turn
fault detector 120 carries out a fault-to-fault detection by taking
this magnetizing current I.sub.0 into consideration in accordance
with the disclosure.
[0051] FIG. 6 illustrates some exemplary elements that can be
contained in the turn-to-turn fault detector 120 in accordance with
the disclosure. For purposes of description, the turn-to-turn fault
detector 120 shown in FIG. 6 contains various elements that can be
used for implementing the exemplary embodiment shown in FIG. 4 and
described above with respect to the three-phase transformer 410.
Accordingly, the input lines and output lines are designated by the
same reference numerals that are shown in FIG. 4. However, in other
implementations, such as, for example, when implementing the single
phase transformer 310 embodiment shown in FIG. 3, the number of
various elements (such as, for example, the number of input
interfaces) contained in the turn-to-turn fault detector 120 can be
different. Furthermore, some elements such as communication ports
and user input/output interfaces that are not shown can be
incorporated into the turn-to-turn fault detector 120 in accordance
with the disclosure.
[0052] In this exemplary implementation, the turn-to-turn fault
detector 120 can include six input current interfaces 605, 625,
645, 620, 640 and 660 that are coupled to lines 404, 406, 407, 408,
409 and 411 respectively. Other input interfaces, such as for
example voltage input interfaces (not shown) can be used for
providing the turn-to-turn fault detector 120 with various kinds of
voltage measurement inputs. The turn-to-turn fault detector 120 can
also include one or more output interfaces (such as an output
interface 665 that is shown coupled to the line 412), for purposes
of transmitting output signals such as a control signal, a fault
indication signal, or an alarm signal.
[0053] The turn-to-turn fault detector 120 can further include one
or more analog-to-digital converters and digital-to-analog
converters. For example, the analog-to-digital converter 615 can be
used to convert a current measurement provided by one of the input
interfaces in an analog form into a digital current measurement
value that can be processed by the processor 650. Conversely, the
digital-to-analog converter 635 can be used to convert various
types of digital information that can be provided by the processor
650 to the digital-to-analog converter 635, into an analog output
signal that is transmitted out of the turn-to-turn fault detector
120 via the output interface 665. One or more relays, such as a
relay 655, can be used for switching various types of signals (such
as, for example, certain current signals associated with the power
transmission system 400) when a turn-to-turn fault is detected in
the three-phase transformer 410.
[0054] One or more processors, such as the processor 650, can be
configured to interact with a memory 630. The processor 650 can be
implemented and operated using appropriate hardware, software,
firmware, or combinations thereof. Software or firmware
implementations can include computer-executable or
machine-executable instructions written in any suitable programming
language to perform the various functions described. In one
embodiment, instructions associated with a function block language
can be stored in the memory 630 and executed by the processor
650.
[0055] The memory 630 can be used to store program instructions
that are loadable and executable by the processor 650, as well as
to store data generated during the execution of these programs.
Depending on the configuration and type of the turn-to-turn fault
detector 120, the memory 630 can be volatile (such as random access
memory (RAM)) and/or non-volatile (such as read-only memory (ROM),
flash memory, etc.). In some embodiments, the memory devices can
also include additional removable storage (not shown) and/or
non-removable storage (not shown) including, but not limited to,
magnetic storage, optical disks, and/or tape storage. The disk
drives and their associated computer-readable media can provide
non-volatile storage of computer-readable instructions, data
structures, program modules, and other data. In some
implementations, the memory 630 can include multiple different
types of memory, such as static random access memory (SRAM),
dynamic random access memory (DRAM), or ROM.
[0056] The memory 630, the removable storage, and the non-removable
storage are all examples of non-transient computer-readable storage
media. Such non-transient computer-readable storage media can be
implemented in any method or technology for storage of information
such as computer-readable instructions, data structures, program
modules or other data. Additional types of non-transient computer
storage media that can be present include, but are not limited to,
programmable random access memory (PRAM), SRAM, DRAM, ROM,
electrically erasable programmable read-only memory (EEPROM),
compact disc read-only memory (CD-ROM), digital versatile discs
(DVD) or other optical storage, magnetic cassettes, magnetic tapes,
magnetic disk storage or other magnetic storage devices, or any
other medium which can be used to store the desired information and
which can be accessed by the processor 650. Combinations of any of
the above should also be included within the scope of non-transient
computer-readable media.
[0057] Turning to the contents of the memory 630, the memory 630
can include, but is not limited to, an operating system (OS) and
one or more application programs or services for implementing the
features and aspects disclosed herein. Such applications or
services can include a turn-to-turn fault detection module (not
shown). In one embodiment, the turn-to-turn fault detection module
can be implemented by software that is provided in configurable
control block language and is stored in non-volatile memory. When
executed by the processor 650, the performance turn-to-turn fault
detection module implements the various functionalities and
features described in this disclosure.
[0058] FIGS. 7A and 7B illustrate an example flowchart of a method
of using a turn-to-turn fault detection to detect a fault in one or
more windings of a three-phase shunt reactor in accordance with an
exemplary embodiment of the disclosure. The three-phase power line
system 100 shown in FIG. 1 will be used here solely as a matter of
convenience to describe the various operations shown in this
example flowchart.
[0059] In block 705, a first phase current measurement that is
based on monitoring a first phase current flowing through a first
winding of the three-phase shunt reactor is received. This
operation can correspond to the turn-to-turn fault detector 120
receiving the first phase current measurement via line 109 from the
first current monitoring element 125.
[0060] In block 710, a second phase current measurement that is
based on monitoring a second phase current flowing through a second
winding of the three-phase shunt reactor is received. This
operation can correspond to the turn-to-turn fault detector 120
receiving the second phase current measurement via line 111 from
the second current monitoring element 130.
[0061] In block 715, a third phase current measurement that is
based on monitoring a third phase current flowing through a third
winding of the three-phase shunt reactor is received. This
operation can correspond to the turn-to-turn fault detector 120
receiving the third phase current measurement via line 112 from the
third current monitoring element 135.
[0062] In block 720, a first phase voltage measurement that is
based on monitoring a first phase voltage present on a first power
line conductor of a three-phase power line system is received. This
operation can correspond to the turn-to-turn fault detector 120
receiving the first phase voltage measurement via line 106 from the
first voltage monitoring element 105.
[0063] In block 725, a second phase voltage measurement that is
based on monitoring a second phase voltage present on a second
power line conductor of a three-phase power line system is
received. This operation can correspond to the turn-to-turn fault
detector 120 receiving the second phase voltage measurement via
line 107 from the second voltage monitoring element 110.
[0064] In block 730, a third phase voltage measurement that is
based on monitoring a third phase voltage present on a third power
line conductor of a three-phase power line system is received. This
operation can correspond to the turn-to-turn fault detector 120
receiving the third phase voltage measurement via line 108 from the
third voltage monitoring element 115.
[0065] In block 735, the turn-to-turn fault detector uses each of
the first phase current measurement, the second phase current
measurement, the third phase current measurement, the first phase
voltage measurement, the second phase voltage measurement, and the
third phase voltage measurement to detect the turn-to-turn fault in
at least one of the first winding, the second winding, or the third
winding of the three-phase shunt reactor. The detection is carried
out by calculating a difference value between a voltage-based
parameter and a current-based parameter, wherein the voltage-based
parameter is indicative of a normalized negative voltage imbalance
and the current-based parameter is indicative of a normalized
negative current imbalance.
[0066] In block 740, the turn-to-turn fault detector declares the
turn-to-turn fault in at least one of the first winding, the second
winding, or the third winding of the three-phase shunt reactor when
the difference value is not equal to zero.
[0067] FIGS. 8A and 8B illustrate an example flowchart of a method
of using a turn-to-turn fault detection to detect a turn-to-turn
fault in one or more windings of a transformer in accordance with
an exemplary embodiment of the disclosure. The power transmission
system 300 shown in FIG. 3 will be used solely as a matter of
convenience to describe the various operations shown in this
example flowchart. It should be however understood that the method
can be suitably applied to detect a turn-to-turn fault in one or
more windings of a multi-phase transformer such as the three-phase
transformer 410 shown in FIG. 4.
[0068] In block 805, a first current measurement that is based on
monitoring a primary winding of a transformer is received. This
operation can correspond to the turn-to-turn fault detector 120
receiving the first current measurement via line 301 from the first
current monitoring element 305.
[0069] In block 810, a second current measurement that is based on
monitoring a secondary winding of a transformer is received. This
operation can correspond to the turn-to-turn fault detector 120
receiving the second current measurement via line 302 from the
second current monitoring element 315. In block 815, each of the
first current measurement and the second current measurement is
used to determine a steady-state differential current value and a
steady-state voltage value. In block 820, one or more compensating
factors are determined by dividing the steady-state differential
current value by the steady-state voltage value. In block 825, a
magnetizing current amplitude indicator is determined by
multiplying the steady-state voltage value with the compensating
factor. In block 830, a compensated differential current value is
determined by combining the steady-state differential current value
with a modifier value, the modifier value incorporating the
magnetizing current amplitude indicator. In block 835, the
compensated differential current value is compared against a
threshold value. In block 840, an occurrence of a turn-to-turn
fault in the transformer is declared when the compensated
differential current value exceeds the threshold value. In block
845, a remedial operation comprising at least one of transmitting
an alarm or operating a protection relay is executed. For example,
the turn-to-turn fault detector 120 can activate the first
protection element 320 and/or the second protection element
325.
[0070] In summary, the systems and methods disclosed herein for
detecting turn-to-turn faults are not limited exclusively to a
transformer as embodied in the accompanying claims, but are equally
applicable to various other objects that incorporate one or more
windings. A few example systems and methods that can be associated
with a three-phase shunt reactor for example, are provided
below.
[0071] A first exemplary system in accordance with an embodiment of
the disclosure is a three-phase power line system that can include
a first power line conductor, a second power line conductor, a
third power line conductor, a three-phase shunt reactor, a first
electrical current monitoring element, a second electrical current
monitoring element, a third electrical current monitoring element,
a first voltage monitoring element, a second voltage monitoring
element, a third voltage monitoring element, and a fault detector.
The first power line conductor can transfer power in a first phase,
the second power line conductor can transfer power in a second
phase, and the third power line conductor can transfer power in a
third phase. The three-phase shunt reactor can be coupled to the
three-phase power line system. The first electrical current
monitoring element can be configured to provide a first current
measurement based on monitoring a first phase current flowing
through a first winding of the three-phase shunt reactor. The
second electrical current monitoring element can be configured to
provide a second current measurement based on monitoring a second
phase current flowing through a second winding of the three-phase
shunt reactor. The third electrical current monitoring element can
be configured to provide a third current measurement based on
monitoring a third phase current flowing through a third winding of
the three-phase shunt reactor. The first voltage monitoring element
can be configured to provide a first voltage measurement based on
monitoring a first phase voltage present on the first power line
conductor. The second voltage monitoring element can be configured
to provide a second voltage measurement based on monitoring a
second phase voltage present on the second power line conductor.
The third voltage monitoring element can be configured to provide a
third voltage measurement based on monitoring a third phase voltage
present on the third power line conductor. The fault detector can
be configured to receive and to use each of the first phase current
measurement, the second phase current measurement, the third phase
current measurement, the first phase voltage measurement, the
second phase voltage measurement, and the third phase voltage
measurement to detect a turn-to-turn fault in at least one of the
first winding, the second winding, or the third winding of the
three-phase shunt reactor by executing a procedure. The procedure
can include calculating a difference value between a voltage-based
parameter and a current-based parameter, wherein the voltage-based
parameter is indicative of a normalized negative voltage imbalance
and the current-based parameter is indicative of a normalized
negative current imbalance, and can further include declaring an
occurrence of the turn-to-turn fault in at least one of the first
winding, the second winding, or the third winding of the
three-phase shunt reactor when the difference value is not equal to
zero.
[0072] The voltage-based parameter can be a first normalized value
derived at least in part by comparing a negative sequence voltage
value to a positive sequence voltage value, and the current-based
parameter can be a second normalized value derived at least in part
by comparing a negative sequence current value to a positive
sequence current value. Each of the negative sequence voltage value
and the positive sequence voltage value can be represented in a
vector representation of phase voltages present in the three-phase
power line system. The first normalized value can be indicated as a
first percentage and the second normalized value can be indicated
as a second percentage. The first normalized value can be equal to
the second normalized value when the turn-to-turn fault is not
present in the three-phase shunt reactor. The fault detector can be
further configured to execute a remedial operation upon the
occurrence of the turn-to-turn fault, the remedial action
comprising operating a protection relay. The remedial action can be
executed based on the difference value exceeding a settable
threshold value. The difference value can be defined as at least
one of an absolute numerical value or an angular value, and the
settable threshold value can be correspondingly based on the at
least one of an absolute numerical value or an angular value. The
difference value can be defined as an angular value, and an
identification of the turn-to-turn fault in a particular one of the
first winding, the second winding, or the third winding of the
three-phase shunt reactor can be determined based on the angular
value. The first winding can be identified when the angular value
is substantially equal to about (180 degrees.+-.a tolerance value),
the second winding can be identified when the angular value is
substantially equal to about (-60 degrees.+-.the tolerance value),
and the third winding can be identified when the angular value is
substantially equal to about (+60 degrees.+-.the tolerance
value).
[0073] A second exemplary system in accordance with an embodiment
of the disclosure is a turn-to-turn fault detector that can include
a first input interface, a second input interface, a third input
interface, a fourth input interface, a fifth input interface, a
sixth input interface, and at least one processor. The first input
interface can be configured to receive a first phase current
measurement that is based on monitoring a first phase current
flowing through a first winding of a three-phase shunt reactor,
wherein the first winding is coupled to a first power line
conductor of a three-phase power line system. The second input
interface can be configured to receive a second phase current
measurement that is based on monitoring a second phase current
flowing through a second winding of the three-phase shunt reactor,
wherein the second winding is coupled to a second power line
conductor of the three-phase power line system. The third input
interface can be configured to receive a third phase current
measurement that is based on monitoring a third phase current
flowing through a third winding of the three-phase shunt reactor,
wherein the third winding is coupled to a third power line
conductor of the three-phase power line system. The fourth input
interface can be configured to receive a first phase voltage
measurement that is based on monitoring a first phase voltage
present on the first power line conductor of the three-phase power
line system. The fifth input interface can be configured to receive
a second phase voltage measurement that is based on monitoring a
second phase voltage present on the second power line conductor of
the three-phase power line system. The sixth input interface can be
configured to receive a third phase voltage measurement that is
based on monitoring a third phase voltage present on the third
power line conductor of the three-phase power line system. The
processor can be configured to use each of the first phase current
measurement, the second phase current measurement, the third phase
current measurement, the first phase voltage measurement, the
second phase voltage measurement, and the third phase voltage
measurement to detect a turn-to-turn fault in at least one of the
first winding, the second winding, or the third winding of the
three-phase shunt reactor by executing a procedure that can include
calculating a difference value between a voltage-based parameter
and a current-based parameter, wherein the voltage-based parameter
is indicative of a normalized negative voltage imbalance and the
current-based parameter is indicative of a normalized negative
current imbalance, and can further include declaring a turn-to-turn
fault in at least one of the first winding, the second winding, or
the third winding of the three-phase shunt reactor when the
difference value is not equal to zero.
[0074] The voltage-based parameter can be a first normalized value
derived at least in part by comparing a negative sequence voltage
value to a positive sequence voltage value, and the current-based
parameter can be a second normalized value derived at least in part
by comparing a negative sequence current value to a positive
sequence current value. Each of the negative sequence voltage value
and the positive sequence voltage value can be represented in a
vector representation of phase voltages present in the three-phase
power line system, the first normalized value can be indicated as a
first percentage and the second normalized value can be indicated
as a second percentage. The first normalized value can be equal to
the second normalized value when the turn-to-turn fault is not
present in the three-phase shunt reactor. The difference value can
be defined as at least one of an absolute numerical value or an
angular value, and an identification of the turn-to-turn fault in a
particular one of the first winding, the second winding, or the
third winding of the three-phase shunt reactor can be determined
based on the at least one of the absolute numerical value or the
angular value. The first winding can be identified when the angular
value is substantially equal to about (180 degrees.+-.a tolerance
value), the second winding can be identified when the angular value
is substantially equal to about (-60 degrees.+-.the tolerance
value), and the third winding can be identified when the angular
value is substantially equal to about (+60 degrees.+-.the tolerance
value).
[0075] An example method according to yet another exemplary
embodiment of the disclosure is a method for detecting a
turn-to-turn fault in a three-phase shunt reactor coupled to a
three-phase power line system. The method can include operations
such as receiving a first phase current measurement that is based
on monitoring a first phase current flowing through a first winding
of the three-phase shunt reactor, receiving a second phase current
that is based on monitoring a second phase current flowing through
a second winding of the three-phase shunt reactor, receiving a
third phase current measurement that is based on monitoring a third
phase current flowing through a third winding of the three-phase
shunt reactor, receiving a first phase voltage measurement that is
based on monitoring a first phase voltage present on a first power
line conductor of the three-phase power line system, receiving a
second phase voltage measurement that is based on monitoring a
second phase voltage present on a second power line conductor of
the three-phase power line system, receiving a third phase voltage
measurement that is based on monitoring a third phase voltage
present on a third power line conductor of the three-phase power
line system, and using each of the first phase current measurement,
the second phase current measurement, the third phase current
measurement, the first phase voltage measurement, the second phase
voltage measurement, and the third phase voltage measurement to
detect the turn-to-turn fault in at least one of the first winding,
the second winding, or the third winding of the three-phase shunt
reactor by calculating a difference value between a voltage-based
parameter and a current-based parameter, wherein the voltage-based
parameter is indicative of a normalized negative voltage imbalance
and the current-based parameter is indicative of a normalized
negative current imbalance. A turn-to-turn fault in at least one of
the first winding, the second winding, or the third winding of the
three-phase shunt reactor can be declared when the difference value
is not equal to zero.
[0076] The voltage-based parameter can be a first normalized value
derived at least in part by comparing a negative sequence voltage
value to a positive sequence voltage value, and the current-based
parameter can be a second normalized value derived at least in part
by comparing a negative sequence current value to a positive
sequence current value. The difference value can be defined as at
least one of an absolute numerical value or an angular value, and
an identification of the turn-to-turn fault in a particular one of
the first winding, the second winding, or the third winding of the
three-phase shunt reactor can be determined based on the at least
one of the absolute numerical value or the angular value. The first
winding can be identified when the angular value is substantially
equal to about (180 degrees.+-.a tolerance value), the second
winding can be identified when the angular value is substantially
equal to about (-60 degrees.+-.the tolerance value), and the third
winding can be identified when the angular value is substantially
equal to about (+60 degrees.+-.the tolerance value).
[0077] Many modifications and other embodiments of the example
descriptions set forth herein to which these descriptions pertain
will come to mind having the benefit of the teachings presented in
the foregoing descriptions and the associated drawings. Thus, it
will be appreciated the disclosure may be embodied in many forms
and should not be limited to the exemplary embodiments described
above. Therefore, it is to be understood that the disclosure is not
to be limited to the specific embodiments disclosed and that
modifications and other embodiments are intended to be included
within the scope of the appended claims. Although specific terms
are employed herein, they are used in a generic and descriptive
sense only and not for purposes of limitation.
* * * * *